Absence of a Quadratic Term in the 4He Excitation Spectrum

  • P. R. Roach
  • B. M. Abraham
  • J. B. Ketterson
  • M. Kuchnir

Abstract

For many years it has been assumed that the long-wavelength portion of the 4He elementary excitation spectrum could be described by
$$\varepsilon \left( k \right)=c\hbar k\left( 1+{{\alpha }_{2}}{{k}^{2}}+... \right)\varepsilon \left( k \right)=c\hbar k\left( 1+{{\alpha }_{2}}{{k}^{2}}+... \right)$$
(1)
where e is the energy of the excitation, k is its wave number, and c is the sound velocity; α2 is traditionally taken to be negative. Recently, however, Barucchi et al.1 predicted that the excitation spectrum could be described by
$$\varepsilon \left( k \right)=c\hbar k\left( 1+{{\alpha }_{1}}k+{{\alpha }_{2}}{{k}^{2}}+... \right)$$
(2)
and Molinari and Regge2 suggested that an improved fit to the inelastic neutron scattering data’ for the excitation spectrum could be achieved with this expression; α1 was positive in the resultant fit.†

Keywords

Quartz Attenuation Helium 

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References

  1. 1.
    G. Barucchi, G. Ponzano, and T. Regge (to be published).Google Scholar
  2. 2.
    A. Molinari and T. Regge, Phys. Rev. Lett. 26, 1531 (1971).ADSCrossRefGoogle Scholar
  3. 3.
    R.A. Cowley and A.D.B. Woods, Can. J. Phys. 49, 177 (1971).ADSCrossRefGoogle Scholar
  4. 4.
    C.H. Anderson and E.S. Sabisky, Phys. Rev. Lett. 28, 80 (1972).ADSCrossRefGoogle Scholar
  5. 5.
    E.S. Sabisky, private communication.Google Scholar

Copyright information

© Springer Science+Business Media New York 1974

Authors and Affiliations

  • P. R. Roach
    • 1
  • B. M. Abraham
    • 1
  • J. B. Ketterson
    • 1
  • M. Kuchnir
    • 1
  1. 1.Argonne National LaboratoryArgonneUSA

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